[GitHub] [hadoop-ozone] amaliujia commented on a change in pull request #1314: HDDS-3988: DN can distinguish SCMCommand from stale leader SCM

[GitBox <gi...@apache.org>]

amaliujia commented on a change in pull request #1314:
URL: https://github.com/apache/hadoop-ozone/pull/1314#discussion_r485371150



##########
File path: hadoop-hdds/server-scm/src/test/java/org/apache/hadoop/hdds/scm/ha/MockSCMHAManager.java
##########
@@ -78,8 +79,8 @@ public void start() throws IOException {
    * {@inheritDoc}
    */
   @Override
-  public boolean isLeader() {
-    return isLeader;
+  public Optional<Long> isLeader() {

Review comment:
       another challenge is how to test such change. ideally we can have a minicluster setup with configurable nodes so we can simulate the scenario of split brian.  

##########
File path: hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/StateContext.java
##########
@@ -478,7 +551,26 @@ public void execute(ExecutorService service, long time, TimeUnit unit)
   public SCMCommand getNextCommand() {
     lock.lock();
     try {
-      return commandQueue.poll();
+      initTermOfLeaderSCM();
+      if (!termOfLeaderSCM.isPresent()) {
+        return null;      // not ready yet
+      }
+
+      while (true) {
+        SCMCommand<?> command = commandQueue.poll();
+        if (command == null) {
+          return null;
+        }
+
+        updateTermOfLeaderSCM(command);
+        if (command.getTerm() == termOfLeaderSCM.get()) {

Review comment:
       I am confused on when `termOfLeaderSCM` is updated to the newest leader term. Is `termOfLeaderSCM` updated in during leader selection? 




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